test:
1. run app1
# app_test1&
hello world
2. run app2
# app_test2&
hello world
3. trigger suspend, app_test1 & app_test2 suspend before system suspended
# pm-suspend
[ 47.070981] EXT4-fs (mmcblk0p7): re-mounted. Opts: data=ordered,commit=0
Message has noargs
app_test1 suspending
app_test1 suspend succeed
Message has noargs
app_test2 suspending
app_test2 suspend succeed
[ 47.617531] PM: suspend entry 1970-01-01 00:00:47.609591605 UTC
[ 47.617606] PM: Syncing filesystems ... done.
4. press the power key, trigger resume, app_test1 & app_test2 resume after system resume
[ 47.721493] PM: resume of devices complete after 8.996 msecs
[ 47.722073] [BT_RFKILL]: ** disable irq
[ 47.723942] Restarting tasks ... done.
[ 47.724748] PM: suspend exit 1970-01-01 00:00:58.589742402 UTC
resume irq: 38
app_test1 resumeing
[ 47.870414] dwc2 ff400000.usb: new device is high-speed
app_test1 resume succeed
[ 47.925415] dwc2 ff400000.usb: new device is high-speed
resume irq: 38
app_test2 resumeing
[ 47.963233] dwc2 ff400000.usb: new address 8
[ 47.982570] android_work: sent uevent USB_STATE=CONNECTED
[ 48.002742] configfs-gadget gadget: high-speed config #1: b
app_test2 resume succeed
